Anterior Cruciate Ligament Tears: Understanding ACL Tears

Anterior Cruciate Ligament Tears: Understanding ACL Tears

[Leeann Harridsleff, PA-C] Today we will be discussing ACL or anterior cruciate ligament tears. To best understand this common injury, we will review the relevant anatomy and understand its role in the knee with the evaluation of this pathology entails. Finally, we will discuss what surgical techniques are available to help restore the stability of the knee when these injuries occur.

To start, the bony anatomy of our knee joint consists of the femur, the tibia, the patella, or kneecap, and the fibula. As we look closer at the end of the femur, we can appreciate how the end of the joint comes into two knuckle-like surfaces, which we call the condyles. The trochlear groove, where our patella glides on the femur, lies between these on the front surface of the femur.

Our ACL attaches to the femur on the inner portion of the lateral condyle of the femur in a space we refer to as the intercondylar notch. We can appreciate this here, again, from a side view of the lateral condyle. When we look inside the intercondylar notch, we can appreciate the anterior and posterior cruciate ligaments named for the way they cross one another on the inside of the joint. These ligaments, paired with others in the knee, help provide stability to the femur and the tibia as we perform activities.

Here is an image of our ACL in a real arthroscopic view. We can appreciate its attachment to the femur and to the front of the tibia in the illustration. The ACL is made up of fibers of collagen running in a linear fashion and cells called fibroblasts and consists of two bundles of these fibers, which work in conjunction during knee motion to help provide stability.

Our ACL is responsible for providing stability to the knee by restraining certain motions. It restricts the tibia from sliding forward away from our femur seen here. The ACL also helps resist rotation of our tibia too far inward towards our midline. And lastly it can help provide stability when forces are applied to the inside and outside portion of the knee seen here labeled as varus and valgus stresses.

So how do we injure our ACL? Well tears can occur from trauma or contact injuries. Typically the injuries are non contact that occur during planting and pivoting sports like soccer, basketball and skiing. They often occur when the leg is placed in a position where the knee is pointed in and the toe is pointed out. ACL injuries make up about 60% of all knee injuries during these kinds of activities and have been found to occur in a higher percentage in females.

When someone has injured their ACL, they may experience a pop sensation and they typically experience immediate pain, swelling, and the feeling of giving way or instability to their knee during turning or pivoting. When a patient presents for evaluation of their knee, this includes a physical exam. This examination test the stability of our knee and can give clues about whether your ligaments have been injured.

Common physical exam tests that might be performed when evaluating for injury of the ACL specifically are the Lachman's maneuver seen here on the left as the surgeon pulls the tibia forward against the femur to test the strength of the ACL, as well as the pivot shift test seen here performed on the right hand side. In addition to a thorough physical exam, the evaluation for an ACL injury may also include an X-ray, which can give clues about the injury.

The best way to evaluate the ACL with imaging is utilizing an MRI scan to evaluate your ACL as well as the other soft tissues of the knee like the meniscus, which may also be affected at the time of injury. When a torn ACL has been determined to require surgical intervention, there are many different factors which affect the treatment options the surgeon may choose. These include the patient's age, activity level, when the injury occurred, and the pattern of the tear.

In some instances, the ACL tears right off the bone where it attaches to. For the right tear patterns, sometimes repairing the patient's own ligament back to the bone and augmenting the repair with a strong suture is a surgical option. During ACL repair, no tissue is taken from the knee and no large sockets are drilled into the bones. In many instances, the ligament cannot be repaired.

When this occurs, the ACL can be reconstructed surgically utilizing tunnels or sockets that are created in the femur and the tibia, placing a graft within these tunnels that span across the joint and fixating the graft into place. The goal of this being to restore the stability of the knee joint that was lost when the original ligament was damaged. ACL reconstruction can be performed arthroscopically, meaning the surgeon can utilize small portals to allow a camera and instrumentation to enter into the joint.

The surgeon can then remove the damaged tissue of the patient's acl and prepare the bone to accept the graft of the surgeon's choice. The graft that the surgeon chooses is ultimately based upon many different patient factors, including their age, activity level, and if they have had surgery previously. Often, the surgeon will use a graph that comes from the patient themselves, which we refer to as an autograft.

These are harvested using small incisions in the area of the tendon being utilized and these options include the patellar tendon on the front of the knee, our hamstrings tendons which live on the medial portion of our knee or inner portion or the quadriceps tendon on the top of the knee. Sometimes the surgeon may decide that the use of a donor graft, which we refer to as allograft, is most appropriate for the patient. These donor grafts go through a treatment process before being utilized to ensure they maintain their strength and are safe to use in patients.

Recovery period following ACL repair or reconstruction will look different for every patient and will depend on the techniques utilized by the surgeon as well as if there were other injuries that were treated during the time of surgery. The goals during recovery include minimizing pain and swelling, protecting the repair or reconstruction that was performed while it heals, and to safely restore the patient's motion and strength of the leg.

Time to return to sports, play and other activities will differ between each patient. So, no matter what technique utilized. The goal of ACL repair or reconstruction is to restore the stability of the knee so that patients can return to the activities that they enjoy. Thank you.